Protein and site specificity of fucosylation in liver-secreted glycoproteins

J Proteome Res. 2014 Dec 5;13(12):5561-9. doi: 10.1021/pr5005482. Epub 2014 Oct 10.


Chronic liver diseases are a serious health problem worldwide. One of the frequently reported glycan alterations in liver disease is aberrant fucosylation, which was suggested as a marker for noninvasive serologic monitoring. We present a case study that compares site specific glycoforms of four proteins including haptoglobin, complement factor H, kininogen-1, and hemopexin isolated from the same patient. Our exoglycosidase-assisted LC-MS/MS analysis confirms the high degree of fucosylation of some of the proteins but shows that microheterogeneity is protein- and site-specific. MSn analysis of permethylated detached glycans confirms the presence of LeY glycoforms on haptoglobin, which cannot be detected in hemopexin or complement factor H; all three proteins carry Lewis and H epitopes. Core fucosylation is detectable in only trace amounts in haptoglobin but with confidence on hemopexin and complement factor H, where core fucosylation of the bi-antennary glycans on select glycopeptides reaches 15-20% intensity. These protein-specific differences in fucosylation, observed in proteins isolated from the same patient source, suggest that factors other than up-regulation of enzymatic activity regulate the microheterogeneity of glycoforms. This has implications for selection of candidate proteins for disease monitoring and suggests that site-specific glycoforms have structural determinants, which could lead to functional consequences for specific subsets of proteins or their domains.

Keywords: MSn structural analysis; N-glycans; exoglycosidase treatment; fucosylation; glycopeptides; hepatocellular carcinoma; mass spectrometry; microheterogeneity; permethylation; site specificity.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Carbohydrate Conformation
  • Carbohydrate Sequence
  • Glycoproteins / blood*
  • Glycoproteins / metabolism
  • Glycosylation
  • Hepatitis C / blood
  • Humans
  • Liver / metabolism*
  • Liver Cirrhosis / blood
  • Liver Cirrhosis / virology
  • Male
  • Middle Aged
  • Molecular Sequence Data
  • Protein Processing, Post-Translational*


  • Glycoproteins